1. Field of the Invention
The present invention relates to a vehicle seat of the type wherein its seat cushion and seat back are operatively interconnected via a linkage arranged among pivotal points associated with the seat cushion, the seat back and a floor of vehicle. The seat back can be folded onto the seat cushion, with the rear surface of the seat back being exposed upside, and thereafter, the seat cushion with the seat back folded thereon be displaced to a storage position, so that the rear surface of the seat back can be used as a loading area or baggage loading area in the vehicle including an automobile.
2. Description of Prior Art
One example of conventional vehicle seats of this kind is disclosed in Japanese Laid-Open Patent Publication 2005-067325 (JP 2005-067325 A1). As shown therein, four pivotal points are defined in the following fashion: i) a lower end portion of a seat back frame is pivotally connected to a seat slide device's upper rail fixed on a floor, thus providing a first pivotal point; ii) a rear end portion of a seat cushion frame is pivotally connected to the seat back frame, thus providing a second pivotal point; iii) a front link is at its upper end pivotally connected to a front end portion of the sea cushion frame, thus providing a third pivotal point; and iv) a lower end of the front link is pivotally secured to the floor, thus providing a fourth pivotal point.
Due to such four pivotal points, a parallel linkage is established among the seat back frame, seat cushion frame, front link, and floor, so that, whenever the seat is folded and moved forwardly and rearwardly, the seat cushion frame and the floor are always maintained in parallel with each other, while the front link and the seat back frame's lower end portion are also always maintained in parallel with each other.
In this sort of seat, however, it is required for a technical designer to set the front link or the afore-said fourth pivotal point within a limited range of positions in order to insure maintaining the parallel linkage described above. Further, the fact that the lower end of the front link has a fixed pivotal connection with the floor necessitates the designer to consider a degree of load that will be directly applied to the front link and adjustingly set a position of the front link's upper end to the seat cushion frame, depending on such degree of load, while insuring that the parallel linkage is maintained. As such, setting a position of the front link to the seat cushion frame and floor (i.e. the third and fourth pivotal points) is actually limited, which means a less freedom of setting the front link thereto, thus limiting a freedom of design for the seat. Moreover, the seat of this Japanese prior art requires forward and rearward sliding of the seat back via upper and lower rails of the seat slide devices to permit forward folding of the seat back onto the seat cushion completely. Consequently, when the upper rail is locked to the lower rail, the seat back is thereby limited as to its forward folding and can be folded at a small angle of inclination, and therefore, under the locked state of seat slide devices, the seat back can not completely be folded down to the seat cushion.